Checking Connections; Replacing The Internal Fuse - Siemens 7UT51 Instruction Manual

17
Installation and Servicing
17.6

Checking Connections

Make sure the circuit breaker for the DC supply is
open.
Check the continuity of all the current transformer
circuits against the plant and connection diagrams:
• Are the current transformers correctly grounded?
• Are the polarities of the current transformer
connections consistent?
• Is the phase relationship of the current
transformers correct?
• Is the assignment of the additional current
transformers IA and IB correct (if used)?
• Are the current transformers IA and IB correctly
grounded (if used)?
• Are the polarities of the current transformers IA
and IB correct (if used)?
If test switches have been fitted in the secondary
circuits, check their function, particularly that in the
"test" position the current transformer secondary
circuits are automatically short-circuited.
Fit a DC ammeter in the auxiliary voltage lead; range
approximately. 1.5 A to 3.0 A.
Check that the relay power switch is in the off position.
Close the battery supply circuit breaker; check polarity
and magnitude of voltage at the terminals or connector
modules.
The measured current consumption should be
insignificant. Transient movement of the ammeter
pointer only indicates the charging current of the
storage capacitors.
Put the miniature slide switch of the front plate in the
"On" position. The unit starts up and, on completion of
the run-up period, the green LED on the front comes
on, the red LED gets off after at most 7 seconds.
Open the circuit breaker for the DC power supply.
Remove DC ammeter; reconnect the auxiliary voltage
leads.
188
Check through the tripping circuits to the circuit
breakers.
Check through the control wiring to and from other
devices.
Check the signal circuits.
Reclose the DC supply circuit breaker.
17.7 Replacing the Internal
Fuse
1. Select a replacement fuse 5 – 20 mm. Ensure that
the rated value, time lag (medium slow) and code
letters are correct.
2. Prepare area of work: Provide conductive surface
for the basic module.
3. Open cover.
4. Loosen the basic module using the pulling aids
provided at the top and bottom.
5. Pull out basic module and place onto the
conductive surface.
6. Remove blown fuse from the holder.
7. Fit new fuse into the holder.
8. Insert basic module into the housing; ensure that
the releasing lever is pushed fully to the left before
the module is pressed in.
9. Firmly push in the module using the releasing
lever.
10. Close cover.
11. Switch on the device again. If a power supply
failure is still signalled, a fault or short-circuit is
present in the internal power supply. The device
should be returned to the factory.
7UT51 v3
PRIM-2330C